the pediatric epilepsy project affords a unique and unequaled opportunity to study central questions of neurolinguistics and cognitive neuroscience. The specific objectives of the research proposed in project #2 are to elucidate the effects of first language acquisition of neurological disease associated with catastrophic epilepsy in children with surgical intervention in childhood for the treatment of these diseases. The research proposed herein focusses on 4 issues: 1) the capacity of each hemisphere alone to subserve language acquisition, 2) the development of lateralization and localization of grammar, 3) maturational constraints on grammar acquisition, and 4) linguistic theory-internal questions regarding the nature of grammar construction and linguistic processing. To address the first question we will study the linguistic development of children undergoing hemispherectomy of either hemisphere. We will compare left vs right hemispherectomy cases with each other and with normal controls. To address the second question, we will compare the effects on linguistic growth of a population of children undergoing left and right resections, matched on a number of relevant indices. Question #3 will be addressed by examining the effects of age on acquisition of grammar re symptom and disease onset and age at surgery for both hemispherectomy and resection cases. Question #4 will be examined by investigating deviance vs delay in the patterns of grammar acquisition, and representation vs processing issues. Documentation and assessment of linguistic growth will be carried out pre-surgically, 6 months post-surgery, 12 months post-surgery, 2 years post-surgery, and 3 years post-surgery (and with additional funding for a longer window of study, 5, 7, and 10 years post-surgery). Data collection will include audio taperecording of spontaneous speech, formal testing of lexical, syntactic, and morphological comprehension and production, and grammaticality judgments. In addition to the information gained specifically regarding the effects of catastrophic epilepsy on language development and the neurological basis of language acquisition and hemispheric specialization for language, this research promises to provide unprecedented information and insight into our understanding of the association between specific patterns of linguistic deficits and patterns of neuropathology in the pediatric epileptic brain. Such findings could provide a useful model for other studies attempting to map brain and behavior -- the ultimate goal of cognitive neuroscience.